1. Field of the Invention
The present invention relates to removable forms for use in pouring concrete walls, and more particularly to high strength forms resistant to bending and to forms which are light weight and which provide for thermal insulation of concrete poured between such forms.
2. Description of the Prior Art
Removable forms are frequently used to form poured concrete walls of basements or buildings. Such forms are frequently used repeatedly and must withstand substantial wear and abuse during handling and shipping. Concrete construction forms must also be very rigid to avoid bending when subjected to static pressure generated by the concrete when it is poured between the forms.
To accomodate the requirements that such forms be durable and resistant to bending, prior art forms have generally been constructed from steel, iron, wood or aluminum. Such forms have the disadvantage that they are relatively heavy and difficult to manipulate. Consequently, handling of the forms becomes time consuming and labor intensive, and concrete casting comprises a substantial part of the cost of building construction.
In colder climates, construction is frequently limited because cold ambient temperatures will result in premature curing of the poured concrete or freezing of the poured concrete before it has a chance to completely cure. To prolong the work season of concrete contactors and others involved in pouring concrete for construction purposes, there have been attempts to facilitate complete curing of the concrete by insulating the concrete after it is poured. During the curing process of concrete, hydrolysis results in chemical exothermic generation of heat. Accordingly, if the concrete can be sufficiently insulated against loss of heat, complete curing of the concrete can be achieved even at atmospheric temperatures well below 32.degree. F.
Numerous prior art methods have been used to prevent heat loss from the concrete. For example, the poured concrete and forms are frequently covered with layered straw or sheet material such as large sheets of plastic. Some concrete forms have also been constructed to have insulation means integrally included. See, for example, U.S. Pat. No. 3,144,701, issued Aug. 18, 1964 to Bowden. The structure shown in the Bowden patent, however, does not provide sufficient insulation nor insulation evenly distributed across their surface area. Accordingly, such forms further require electrical heating devices. Such heating devices are cumbersome, require the availability of an electrical power supply and require the use of a substantial amount of electrical power during the curing cycle of the concrete.